980 hours on engines - compression test

[Scott Danforth]

Questions are good, discussions and banter are good too. a really good site on BBC and SBC info is Grumpys Garage.

hundreds of hours of reading

general link http://garage.grumpysperformance.com/index.php#the-engine-shop-non-year-specific.49

applicable links:

http://garage.grumpysperformance.com/index.php?threads/chevy-big-block-vi.9857/

http://garage.grumpysperformance.com/index.php?threads/forged-or-not.13226/

http://garage.grumpysperformance.com/index.php?threads/salvaging-marine-engine-blocks.2300/

http://garage.grumpysperformance.com/index.php?threads/checking-blocks-heads-for-cracks.3363/

 

[tpenfield]

Thanks for the links :thumb:

 

[tpenfield]

I have been reading up on some of the 'grumpys' links provided and various other sources. . .

Most recently about the whole issue about torque plates for boring and honing . . . It seems that the head bolt torque distorts areas of the cylinder wall when the cylinder heads are installed . . . seems logical that there would be some distortion.

I would assume that the distortion is focused on the five (5) areas where the head bolts attach to the engine block, and that the distortion is the result of the head bolts pulling upwards on the deck which tends to pull the cylinder wall radially outward increasing the bore diameter in that general area. So, the bore is no longer 'true' once the bolts are tightened.

According to Internet folk lore, the distortion can be several thousands of an inch (0.002" - 0.003") whereas the tolerance for out of round and taper are only about 0.001".

I assume that the original boring of the engine block at the factory is not done with the benefit of a torque plate. There are varying opinions about using a torque plate or not using one. . . . :noidea: High performance rebuilds - yes, general purpose rebuilds - not really needed. Thoughts?

I am wondering if Gen 6 blocks are any better (or worse) in terms of distortion than the earlier Mark IV blocks

I was thinking that when I take apart the engines, I could take apart the 'bottom' of the engine first, leaving the cylinder heads intact, remove the crankshaft & pistons, and then take some measurements of the cylinder bores while the heads are still on and torqued, particularly noting the areas of the bolt heads. Then re-measure once I have the heads removed to see what the differences are.

My understanding is that normal bore measurements would be 2 'diameter' measurements at 90 degree angles to one another, at the top, middle, and bottom of the cylinder (6 measurements total for each cylinder) . . . Correct? I could probably see if I can identify the bolt head distortion areas with a bore gauge. Then re-measure once the heads are off.

Any thoughts and advise on cylinder bore measurement and the idea of measuring the bore 'from the bottom up' while the heads are still on ??? :noidea:

 

[achris]

You can't pull the pistons out through the bottom of the block... They don't fit...

Chris...

 

[tpenfield]

You can't pull the pistons out through the bottom of the block... They don't fit...

Chris...

I did not know that. I thought that they might be able to come out, but good to know otherwise. Looks like I'll be pulling the heads to do the measurements.

 

[Scott Danforth]

I was thinking that when I take apart the engines, I could take apart the 'bottom' of the engine first, leaving the cylinder heads intact, remove the crankshaft & pistons, and then take some measurements of the cylinder bores while the heads are still on and torqued, particularly noting the areas of the bolt heads. Then re-measure once I have the heads removed to see what the differences are.

if you had a flat-head ford, you can stuff pistons thru the bottom

on a BBC.....no way unless you use det-chord

you gotta pull da heads

 

[Scott Danforth]

pull the head, rotate motor to bottom take measurements of what you can.

measure the ridge at top, if your finger nail catches it, time for rebuild

 

[tpenfield]

I found some interesting comments on the 'grumpy' website about the Gen 6 BBC engine block . . .

"GEN VI blocks all have 4-bolt mains, priority main oiling and leak resistant 1-piece rear main seals. These cylinder cases have revised cylinders in either siamesed or open configuration and they provide thicker cylinder wall and deck surfaces for greater stability. They accept all common big block cylinder heads and they incorporate a fully machined fuel pump pad and provisions for either hydraulic or flat tappet lifters."

These seem to be good things vs. the older bbc blocks.

 

[alldodge]

Measuring the bores without removing the pistons can give you some numbers, but not so sure this will give you the full picture. Need to measure below where the rings stop to get full reading, but would give you some info

torque plate boring is always best, and using a torque plate just to measure and old bore (not a fresh one) I would not recommend. The heads have a a different flatness (in most cases) then the original old head.

 

[tpenfield]

Thanks, AD. Based on Scott's and Chris' comments, I'll just take the whole thing apart (top and bottom) to measure the full extent of the cylinder bores as well as the crank and cam journals. This should give me the direction on machining, etc.

 

[Scott Danforth]

youre talking yourself into a rebuild that I dont believe you need. start with pullin the intake manifold and the heads. then inspect if you need to go further. my guess you find good cross-hatch and no ridge...

 

[tpenfield]

You're talking yourself into a rebuild that I don't believe you need. start with pulling the intake manifold and the heads. Then inspect if you need to go further. My guess you find good cross-hatch and no ridge...

Understood. I do want to get some measurements off of the crank and cam shafts to see how close they are to their service tolerances.

 

[tpenfield]

I took advantage of some cyber Monday shopping a couple weeks back. Got some micrometers and other measuring tools.

Just getting used to using them. I got a digital and an analog mic, to measure to 1/10,000 th of an inch. I wanted to see how accurate/consistent the two mic's were, so I measured a few things.

they seem very accurate, or at least consistent.

As an example, I measured this mechanical pencil body.

The digital mic said it was 0.3062" . . . the analog mic said 0.3062"
.

.
Kind of amazing to be consistent to 0.0001" :thumb:

 

[harringtondav]

I assume that the original boring of the engine block at the factory is not done with the benefit of a torque plate. There are varying opinions about using a torque plate or not using one. . . .

Here in Waterloo IA JD doesn't use torque plates on their diesel block line, but they use cylinder liner sleeves. So, no help. It does make for a simpler rebuild though.

Since it looks like you'll be all over those engines with a bore gauge, maybe take and extra set of measurements with and w/o the heads torqued on. That should give an idea if distortion will be an issue.

 

[achris]

.... I got a digital and an analog mic, ...

Never bothered with digital gauges. I have both vernier and micrometer, both 'mechanical'... Reading vernier scales isn't that difficult, but finding a new battery at 7pm can be... One thing that may also be worth doing is measuring the quiescent current of the digital gauge. May may be at just how much they eat batteries when doing nothing. ie, have plenty of spare batteries available!

BTW. I'd trust a mechanical instrument over a digital every day of the week. And, digital gauges can vary their displayed readings as battery voltage drops.

Chris.........

 

[Lou C]

Ted have you considered just putting the boat up on the market in the spring to gauge interest and what an interested buyer would pay? It just seems like a lot of trouble to go through, for an un-known payoff. I'm just thinking of the things that can go wrong, etc. If I did such a project, then for sure it would be because I intended to keep the boat long term. If you are thinking of selling (I think you said you were) I would not do this project. There is risk and the payoff is not a given.
I plan to run my old boat a few more years (if my partial rebuild lasts that is) and then when it acts up again I have a decision to make...re-man engine time, or sell as is. Same thought process. You sold your other Formula as is and if I recall it sold pretty fast. Unless you really WANT to do the project for the learning experience and increase in knowledge, which of course we all understand being on this and other sites, but usually those projects don't exactly make financial sense, lol!

 

[tpenfield]

Ted have you considered just putting the boat up on the market in the spring to gauge interest and what an interested buyer would pay? It just seems like a lot of trouble to go through, for an un-known payoff. I'm just thinking of the things that can go wrong, etc. If I did such a project, then for sure it would be because I intended to keep the boat long term. If you are thinking of selling (I think you said you were) I would not do this project. There is risk and the payoff is not a given.
I plan to run my old boat a few more years (if my partial rebuild lasts that is) and then when it acts up again I have a decision to make...re-man engine time, or sell as is. Same thought process. You sold your other Formula as is and if I recall it sold pretty fast. Unless you really WANT to do the project for the learning experience and increase in knowledge, which of course we all understand being on this and other sites, but usually those projects don't exactly make financial sense, lol!

Probably keeping the boat for 3-4 more years. Saving up for the next boat, which will be in the $150K range (I think). So I figure it would be worth the rebuild in case my plans get delayed. :noidea:

If I sold the boat now, I would not be able to buy the boat I want (with cash, which is kind of a rule I have for buying boats )

 

[harringtondav]

BTW. I'd trust a mechanical instrument over a digital every day of the week.
Chris.........

Maybe, if you own the results of your measurements. I set up the gauging for dozens of +- .013 mm production tolerances. Mitutoyo, Mahr and Federal Maxum digital kept it simple for 12 guys making parts over three shifts. Veneer mics and calipers don't lie, if your eyes are good. Dial anything is a gear driven clockwork, and not to be trusted if you're living below a thou.

I'm curious how tpenfield is going to get accurate bore sizes. A dial bore gage needs gage blocks or a large micrometer to set it for cylinder bores. They're OK with size and taper. A little iffy on roundness.

 

[tpenfield]

I'm curious how tpenfield is going to get accurate bore sizes. A dial bore gage needs gage blocks or a large micrometer to set it for cylinder bores. They're OK with size and taper. A little iffy on roundness.

Probably with a bore dial indicator thingy Something like this. . .

An interesting thing in the video was to see how the guy in the video rocks the dial gauge back & forth to find when the tool is perpendicular to the cylinder bore.

 

[Lou C]

If you average 40 hrs a year then over 4 years you need to make 160 more hrs on these engines, I'm saying you should be able to make that easily due to the fact that these engines have been closed cooled since you've had the boat and your comp test results are good. With your previous Formula I recall the issue was that it was raw water cooled in the salt and the cyl head rusted through behind the valve seat. So you won't have that concern in this case.

I'm going to run mine till it acts up again and then may just go for a brand new Vortec 4.3 V6. Add closed cooling, electric fuel pump and convert the Quadrajet to an electric choke so I can use it with the Vortec engine (no exhaust cross over on Vortec intake manifolds).